A rack for storing elongate core sample boxes is formed from two separate frames each having three upright posts formed of tubular steel and a plurality of steel tubes extending across between the posts and welded to the posts. The frames can be transported in assembled form and then connected across the top and bottom of the uprights by metal bridging members with C-shaped inserts into the ends of the posts. The structure is held together and braced by diagonal braces which attach to tabs on the bridging members by a wedge drive into a slot in the tab.